Monday, January 31, 2011

January 31, 2011 - Reviewing Matter HW (review for quiz)

When we first got to class, Mr. Finley announced that the quiz that he told us about on Friday will be postponed to Tuesday, February 1. Then, he checked the homework from Friday, and we went over it as a class. The homework was about reviewing matter.

It was about the speed of particles moving, and how particles relate to the different types of energy. For the first question, it was about someone trying to open a jar, and they ran it under hot water. To demonstarte what the particles would do in cold and hot water, Mr. Finley did a demonrtation. 4 people stood in a line, shoulder to shoulder, tightly (they represented particles) and they started to "vibrate". This showed how the speeds of particles change from fast to slow or slow to fast. It also demonstrated how the particles tend to expand from each other.

For another part of the question, we had to draw particle pictures. Below are the ones from class:

The next question related to thermal energy. You had to rub 2 pieces of paper together, and explain why the temperatues incresed. It rose because the particles on each sheet of paper bump into eachother. The internal energy/thermal energy was increasing, as someone said. Next, we had to make a bar chart. 1 sheet of paper was the system, so it was doing work. The bar chart that the class made together was:

**the heating symbol in a bar chart is: Q

The bar chart basically explains:

Intitial: The paper didn't have energy because there was no work/heating being done

Work/Q: The papers were rubbed together, so it created heat

Final: The end showed the same amount of energy that was there while the papers were rubbed together.

Next, we discussed why the temeperature cooled down after it was rubbed. Someone in the class said the energy was transferred to the air (the paper was heating the enviorment). Mr. Finley decided to relate it to real life. So he asked what what we mean when we say "heat". Somebody answered that we mean "hot air". So, this proved that by rubbing two things together, its not making you feel heat, it is really making hot air around the objects, so you feel that. After doing that, we learned how to draw a bar chart with negative thermal/internal energy. It would look like this:

Initial: Some thermal energy

Work/Q: Lose part of the existing thermal energy

Final: Only a little thermal energy left

Finley went back to energy transfers and compared school to it. He said that after school when he is working, and no one is here, it's colder. The energy isn't transferring because there are not any people moving around and causing a lot of energy.

The last part of the homework was the lemonade problem. It was a situation about cold lemonade in hot water. Finley wanted to know why the temperatures became the same. The difference of the hot water transferring energy and the energy steeling energy lead to the temperature change in the lemonade situation. It went from warm to cold which brought us to the 2nd Law of Thermodynamics. The 2nd law is getting an equal lybrium. In this 2nd law, energy always moves from warm to cold (high to low). The first law was the transferring of energy concept.

That was all that we did in class today, but we have homework. It will be posted on Mr. Finley's website. He told us that it is about finding 3 types of heat. Before we left he gave us 2 hints though:

***2 of them start with the letter C, and the other one starts with R.***

1 comment:

Are we suppose to label our bar charts with the initial state on one side of the chart and final state on the other or do we need to do the labels for kinetic energy, gravitational potential energy, and elastic potential energy? -DB